I've broken ribs twice in the past three years. I picked up a little fame on the Clyde forum for breaking a rib during a crash on a bike tour and then riding and camping for two more days before I got medical attention. Don't do that. :-)

You won't lose that much conditioning in six weeks. And besides, you can get it back. As far as exercise goes, like any athlete, only you can determine what level of pain you can handle. So work around your discomfort.

The reason the doctor wants you to avoid cycling is that a second fall can be very dangerous. The rib can fracture again, or break in another spot, or puncture a lung. So be careful.